1. Field of the Invention
The present invention relates to the fabrication of integrated circuit devices, and more particularly, to a method of reducing peeling and cracking of the dielectric layer over a spin-on-glass layer, especially along the wafer edge, in the fabrication of integrated circuits.
2. Description of the Prior Art
Typically, a spin-on-glass (SOG) layer is used to planarize the underlying layers before a dielectric layer such as tetraethoxysilane (TEOS) is deposited. Via openings are made through the TEOS and SOG layers to underlying conductive layers to be contacted. Referring to FIG. 1A, it has been observed that cracks 62 appear especially at the edge of the wafer 5 where the clamping ring holds the wafer in place during etching. The cracking results in peeling of the SOG and TEOS layers and in the presence of trace particles. During the SOG etchback process, CHF polymer buildup occurs especially along the clamping fingers. During subsequent TEOS deposition, pinholes are formed where the polymer has been built up and an organic rich C.sub.x H.sub.x oxide layer is formed at the SOG/TEOS interface. During wet chemical etching to form a via opening, C.sub.x H.sub.x has a very high etch rate so that the wet chemical etchant will punch through the pinholes and the organic rich oxide layer. The organic layer will be etched away leaving the wet chemical etchant at the SOG/TEOS interface. During high temperature sputter deposition of metal to fill the via opening, the wet chemical etchant becomes a vapor which will lift off the TEOS film. Portions of the wafer that are cracked 62 can break when the wafer is again clamped for sputtering of the conducting layer. As illustrated in FIG. 1B, the wafer is broken at crack 63. Trace particles 65 are scattered over the wafer surface.
U.S. Pat. No. 5,003,062 to Yen teaches forming a spin-on-glass sandwich using multiples SOG layers that are baked and vacuum degassed after each deposition to prevent outgassing and cracking of the SOG layers. U.S. Pat. No. 5,334,554 to Lin et al teaches using a nitrogen plasma treatment on the silicon oxide layer underlying the SOG layer in order to prevent a positive charge build up between the SOG and other dielectric layers. U.S. Pat. No. 5,270,267 to Ouellet teaches curing the SOG layers in a plasma which causes an electric field in the SOG film so as to form a film that is very stable in moist air or in water.